Residue Reviews

In manufacturing, formulating, and packaging, workers appear to be adequately protected through the surveillance and mandates of NIOSH, OSHA, and the various concerned state agencies. OSHA is developing a generic pesticide manufacturing standard designed to assure greater safety in the workplace. Shipping and warehousing workers are not yet adequately protected, particularly against accidental spillage or rupture of pesticide containers, with consequent contamination of vehicle, roadside, street, or warehouse. Pesticide fires deserve additional study and attention.

By way of introduction we will give a little background as to how this seminar-workshop entitled “Minimizing occupational exposure to pesticides” came about.

Synthetic organic pesticides when used properly are of tremendous benefit to man and his environment, but when misused or used carelessly, they may cause considerable harm. There is little doubt, however, that pesticides have played, and most likely will continue to play, an important role in the production of food as the world’s supply of raw agricultural products continues to decline in proportion to the increase in population. The use of pesticides in agriculture has increased the cost/benefit ratio for the farmer, and has ultimately reduced the cost of food and fiber products for the consumer. Nevertheless, information about the health of workers occupationally exposed to pesticide residues is still limited even though we have used large quantities of pesticides during the past four decades.

This communication is presented with two objectives in mind. The first objective is to provide an introduction to personnel monitoring of occupational exposure to pesticides for those who are not familiar with this field of investigation. The second objective is to stimulate discussion, which will result in the formation of recommendations for research necessary for material improvement of exposure assessment.

In most instances Cholinesterase determination in people is carried out either: (1) as part of a surveillance procedure to prevent poisoning in people exposed to organophosphorus compounds or (2) as a diagnostic tool to exclude or confirm that symptoms or signs observed in people are caused by anticholinesterase compounds.

Field workers hand harvesting, stripping, thinning, disbudding, pruning, and pinching crops come into contact with toxic organophosphate residues on foliage. These residues inhibit Cholinesterase activity, causing dizziness, pinpoint pupils, nausea, headache, and other symptoms which, if severe enough, lead to hospitalization and/or loss of work. To reduce these hazards, the California Department of Agriculture in 1971 established reentry intervals for 16 organophosphate1 insecticides. This list has been expanded over the last eight years to include 21 organophosphate insecticides used on vine and tree fruits as indicated in Table I.

As is true of toxic substances in general, pesticides pose several different kinds of threats to health. Defined broadly as “adverse effects,” they are commonly considered either acute effects, developing promptly and resolving rapidly, or chronic effects, which may appear after a delay, but then persist for weeks to years.

A reentry standard could be defined as a regulatory measure instituted to limit the exposure of field workers to toxic pesticide residues upon entering previously treated agricultural areas. Included in this definition are (1) those measures designed to reduce the transfer of the toxic residues to the workers, and (2) those measures designed to reduce the residues available for exposure of the workers. Within the first group are protective clothing, gloves, respirators, dust masks, hats, and any other mechanical barriers between the applicator and the pesticide as applied. Within the second group are reentry intervals, spraying of foliage with water, closed system applications, and other means to reduce the pesticide residues. This paper is concerned mainly with reentry intervals.

The occupational exposure of field workers to postapplication insecticide residues in the agricultural setting is referred to as the “reentry problem.” This problem is associated with illnesses precipitated by excessive Cholinesterase depression resulting from exposure to and consequent absorption of persisting residues of the organophosphorus insecticides and their toxic alteration products. The problem is not new. It came into existence hand-in-hand with the introduction in the early 1950s of organophosphorus insecticides into agriculture. The carbamate insecticides have received less emphasis since Cholinesterase inhibition is reversible with these compounds and, consequently, the problem can disappear before it can be unambiguously established for a field population. In addition to protecting workers from acute exposure, the question of health effects arising from chronic exposure also needs to be addressed. This considerably broadens the definition of the reentry problem and encompasses all insecticides since the potential exists that they may be teratogenic, oncogenic, or mutagenic or cause specific problems such as sterility or nerve damage. Information is needed which can be used to assess the potential hazards, if any, that workers are exposed to under actual field conditions, then to mitigate, or somehow compensate for, these hazards.

It has long been recognized that the handling of pesticide materials while preparing spray mixtures can be a primary source of worker exposure in field operations. The means most commonly relied upon to minimize such exposures include precautionary warnings on the label and suggestions or requirements for the use of protective clothing or skin coverings, eye shields, and respirators. While effective to the extent that such safety guidelines and provisions are carefully observed and unfailingly used, worker judgments against the need for certain protective measures and the universal tendency to reject inconvenience have resulted in a continuance of poisoning cases related to such work activities. In California, physicians’ reports analyzed by the State Department of Health and the State Department of Food and Agriculture (1974) show that during the early seventies mixing and loading, in relation to other work activities predisposing to pesticide exposures, were among the categories of activity sustaining the highest incidence of serious exposures exceeded only by the involvements of ground applicators as a grouping at risk.

It is known that pesticide intoxication in agricultural workers is probably the result of excessive dermal exposure to pesticides. Poisonings can occur in applicators from spillage and in field workers due to contamination of clothing by drift and residue (Southwick et al. 1975). Absorption through the skin is perhaps the most important mode of entry of the pesticide into the body during spray applications. Wolfe (1973) found that over 97% of the pesticide to which the body is subjected during possible exposure situations is deposited on the skin.

This paper is intended to provide some viewpoints of the manufacturers of chemical pesticides, although it is realized that no single papelcan adequately represent the views of some 160 manufacturers of almost 1,000 pesticide chemicals and some 35,000 registered products with sales volume in the range of 6 or 7 billion dollars per year.